Organic elemental analyzers are known, for example the Flash 2000 Elemental Analyzer manufactured by Thermo Scientific. In these devices, a thermal conductivity detector is used to compare the conductivity of a portion of the reaction products of a sample material (which passes along a “measurement” channel of the thermal conductivity detector (TCD)) with the conductivity of a reference gas (which passes along a “reference” channel of the thermal conductivity detector). Also known are isotope ratio mass spectrometry (IRMS) elemental analyzers, for example the EA IsoLink IRMS System, which includes the Flash IRMS Elemental Analyzer manufactured by Thermo Scientific. In the EA IsoLink IRMS System, a mass spectrometer is used to measure the isotope ratio of an element in the reaction products of a sample material. The invention will be described primarily in the context of an organic elemental analyzer but it should be understood that the invention is also applicable to elemental analyzers interfaced with IRMS.
The sample of material is provided by an auto-sampler, which can be loaded with multiple samples of one or more material and delivers these into a reactor to undergo reaction. It is important that the sample is not contaminated and so the auto-sampler is supplied with a carrier gas, and the sample material is delivered into the reactor in the presence of the carrier gas. The reactor can be a combustion reactor, combustion/reduction reactor or pyrolysis reactor for example. The products of the reaction, for example CO2, CO, NOx, N2, H2, H2O, and/or SO2, along with the carrier gas are then fed to the measurement channel of the thermal conductivity detector. A reference gas, which may be the same as the carrier gas, is conveyed to the reference channel of the thermal conductivity detector. In this way the amount of reaction products can be measured and hence an elemental content (for example the content of one or more of C, H, N, S and/or O) can be determined. In the case of an IRMS elemental analyzer, the reaction products can be ionised downstream of the reactor (optionally downstream of the TCD where present) and thereafter mass analysed to determine an isotope ratio of one or more reaction products.
To further avoid contamination, it is necessary that the system remains continually supplied with the carrier gas to prevent the contamination of any future experiments with environmental gases.
Typically, other devices will be provided between the reactor and the thermal conductivity detector. For example, the output of the reactor may pass to an adsorption (or absorption) trap for the removal of particular species from the gas stream, for example water, as required by the particular analysis being performed and from there to a separation device such as a chromatography column to separate the reaction products thereby allowing them to pass sequentially to the thermal conductivity detector.
Such systems may be configured for “CHNS determination” (carbon, hydrogen, nitrogen, sulphur) or “O determination” (oxygen). In this context, “CHNS determination” includes any determination of any subset of these elements such as CHN or NCS determinations for example. In each of these configurations, the system requires a different configuration and may use different carrier and reference gases.
It is problematic to re-configure existing systems, which are not flexible and do not allow a variety of different analyses to be scheduled in advance. Consequently, this requires hardware modifications that are time-consuming and reduce the operation time of the instrument and thus reduces significantly laboratory throughput and instrument automation. Moreover, the requirement for a continuous supply of carrier gas when the device is not in use is costly and increasingly problematic in light of the global helium supply shortage relative to very high demand.
There is therefore a need to overcome these disadvantages and provide a more flexible, automated system that may increase sample throughput, may reduce maintenance intervals and may increase automation.